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LARP CM15
Magnet Testing Working Group
SLAC, November 2nd 2010
Outline

Test requirements for the long HQ (consider two cases, 3.3 m coil
length - same as LQ - and 4 m coil length): possible facilities and
required upgrades.

Large diameter probes for field quality measurements: probe
fabrication, anti-cryostat/header modifications, possibility to perform
measurements in LHe

Magnet protection from shorts/ground faults

Electrical QA: status, analysis, etc.

Quench Detection

AOB
Test requirements for the long HQ: possible
facilities and required upgrades
Facilities (FNAL, BNL and CERN)
 3.3-m long HQ coils


Fermilab:
 No upgrades are required for testing from 4.5K to 2.5K.
 Lambda plate is necessary for 1.9K test.
 New warm bore is required for magnetic measurements
BNL:


PS
CERN: Test facility will be ready by March-April 2011
 Cryostat working at 4.5-1.9 K range
 20 kA power supply
 Commissioning of DAQ and control systems
Test requirements for the long HQ: possible
facilities and required upgrades (cont’d)

4-m long HQ coils

BNL

CERN: Test facility will be ready by March-April 2011
Possible Upgrades
 Fermilab:




“Lambda plate” for 30kA top plate
New warm finger with 90-mm outer and 70-mm inner diameter
(estimated cost ~ 20k$, 5-6 months from order placement)
BNL:
CERN:
Large diameter probes for field quality
measurements

What is a reference radius for magnetic measurements?


Define magnetic zone length


CERN asking for 95-mm of free bore diameter ?
Non-connection end, straight part, layer jump, connection end
Large diameter probes

Fermilab:
 Currently using probes have a reference diameter of 46 mm
 New PC board based probes with various reference radius
and length are fabricated (low cost).
 Fabrication of new tangential coils will be much more
expensive and time consuming

BNL:
Large diameter probes for field quality
measurements (cont’d)

Large diameter probes


Anti-cryostat/Header modifications


CERN
Fermilab
 Need new warm bore
 Maximum outer/inner diameter is 90-mm/70-mm
 Need to build new header, lambda plate and warm bore if
more than 90-mm reference diameter is required
Test in LHe
Magnet protection from shorts/ground faults
Fermilab
 Symmetric coil (and heater) grounding

The maximum coil to ground voltage reduced by factor of 2

Ground current through the fault was significantly reduced (from
40 A to about 3 A)
Magnet protection from shorts/ground faults
(cont’d)
Fermilab:
 Active coil ground fault detection

Isolated 5 V voltage source connected in series with the ground
resistor

Voltage drop develop across the
ground resistor (100-Ohm) in case
of coil to ground short

“Always armed”

Should not depend on power supply
voltage and magnet inductance

Is equally sensitive to ground fault at
different locations
Magnet protection from shorts/ground faults
(cont’d)
Fermilab



BNL:


Plan to implement an active heater ground fault system too
Ready to share experience
Plans for the ground fault detection
CERN:
Electrical QA: status, analysis, etc.

Pulse test
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

Initial and after test Hipots

.
Test procedure
Maximum voltage for the test
Fermilab performs Hipot at 1.9K too after first few quenches
Quench Detection

Fermilab




FPGA based quench management system was implemented in
addition to the existed VME based system
Difference of the Half-coil signals are mainly used for quench
detection
Current dependent thresholds implemented for the Half-coil
signal modules both in VME and FPGA based systems
Whole-coil signal also triggers quench

BNL

CERN
What else ?
Documentation:
 Fermilab

Magnet description